Chemotherapy drugs are grouped by their composition and how they destroy cancer cells. Some drugs work best during specific phases of the cell cycle, while others kill cells at all phases. Your oncologist will plan the best timing and dosage of a chemotherapy drug for your treatment. Some of the main classes of chemotherapy drugs are:

• Alkylating agents: These drugs damage DNA, preventing cell division. They are mostly cell cycle phase nonspecific, meaning they kill cells at any phase.
• Antimetabolites: These drugs replace natural substances in DNA, affecting cell metabolism and protein synthesis. They are usually cell cycle phase specific, meaning they kill cells during a particular phase, usually the S phase, where DNA synthesis occurs.
• Antitumor antibiotics: These drugs block an enzyme called topoisomerase, which helps DNA unwind and wind during the cell cycle. They are mostly cell cycle phase nonspecific, meaning they kill cells at any phase.
• Mitotic inhibitors: These drugs stop cell division by interfering with microtubules, which help separate chromosomes during the cell cycle. They are cell cycle phase specific, meaning they kill cells during a particular phase, usually the M phase, where mitosis occurs.
• Targeted therapy: These drugs target specific molecules or pathways that help cancer cells grow and survive, such as receptors, enzymes, or genes. They are more selective and less toxic than conventional chemotherapy drugs, but may still cause side effects.